This invention relates to a differential for a motor vehicle, and more particularly, to a differential for the axle drive of a motor vehicle, including a differential case carrying a driving wheel. An axle bolt is disposed in the differential case which carries differential gears. These differential gears mesh with axle shaft gears arranged on axle drive shafts. These axle shaft gears are constructed as bevel gears, and are disposed in a cage, absorbing forces acting in the direction of the axle drive shafts.
German Patent document P 43 13 322.3 illustrates and describes a differential for the axle drive of a motor vehicle in the case of which the axle shaft gears are disposed in a cage. This cage absorbs the forces acting in the direction of the axle drive shafts. This frees the differential case from these forces. The differential case can, therefore, have smaller dimensions. This separate cage permits the insertion of the axle shaft gears and the axle bolt before the whole differential is mounted.
It is an object of the present invention to further develop such a differential so that the cage is optimized with respect to its stiffness, has a light weight, is low in cost and is easy to manufacture and mount. According to the present invention, this object is achieved by a differential for the axle drive of a motor vehicle, including a differential case carrying a driving wheel. An axle bolt is disposed in the differential case which carries differential gears. These differential gears mesh with axle shaft gears arranged on axle drive shafts. These axle shaft gears are constructed as bevel gears, and are disposed in a cage, absorbing forces acting in the direction of the axle drive shafts. The cage is made of a tube section whose wall has at least two diametrical bores through which the axle drive shafts are lead.
If, in the case of a differential of the above-mentioned type, the cage consists of a tube section whose wall has at least two diametrical bores for the lead through of the axle drive shafts, particularly during series production, this tube section can be manufactured by dividing a prefabricated or commercially available tube, without any high losses of material. Because of the favorable course of the tension, the wall thickness of such a tube section may be kept relatively narrow so that the corresponding cage is relatively light. In an additional or parallel operating step, at least two diametrical bores through which the axle drive shafts are led are provided in this tube section. A joining or connecting of the cage, as in the case of the cage according to the German Patent document P 43 13 322.3, is not required so that, on the one hand, an additional manufacturing step is saved and, on the other hand, a connecting point having an altered stability is avoided.
In an advantageous embodiment, the differential or its cage can be improved if the cage consists of a cylindrical tube section which is changed to a spherical shape through a deformation operation. This deformation operation is preferably carried out in a non-cutting manner via expanding or rolling round. This deforming operation improves the course of tension in the cage. This is because tension peaks are avoided by eliminating small curvature and corner radii. At the same time, the bearing of the axle shaft gears is improved, since these gears can be supported in the shape of a spherical segment on the cage. As a result of this improvement of the shape and of the course of the tension, the wall thickness of the cage can again be reduced so that its weight can be further reduced.
Particularly for average driving power situations, and correspondingly low driving and reaction forces in the differential, the weight of the case can be again reduced if two additional diametrical bores are provided which extend approximately at a right angle to those of the axle drive shaft and by which the axle bolt is guided.
For high driving power situations and correspondingly high reaction forces in the differential, this differential or the cage can be improved in an advantageous further embodiment by providing the cage with a rectangular cross-section having rounded corners and a stress-specifically adapted wall thickness. As a result of the stress-specific and tension-optimized wall thicknesses of the cage, this cage can be optimized with respect to its weight as well as its stability. The stress-specifically adapted wall thickness and the rounding of the corners result in optimal stabilities and an optimal course of tension while avoiding tension peaks. This type of a rectangular profile or square tube profile can be produced in a simple and advantageous manner from an extruded profile.
A cage of this type having a rectangular or square cross-section may be further improved by curving the walls with the bores for guiding the axle drive shafts toward the inside in the installed condition. As a result, an improved defined supporting behavior and a spring effect are obtained for minimizing the load peaks. Furthermore, for low loads and correspondingly low reaction forces or supporting forces, because of this curvature toward the inside, a lubricating gap construction is achieved through which lubricant can reach the bevel gear guide area.
The mounting and the assembly of the differential are facilitated when the axle bolt is surrounded by a guide ring which is arranged between the differential bevel gear and a stop surface. The guide ring has guide extensions which are supported on the cage and guide the cage and the axle bolt relative to one another. By using this guide ring, on the one hand, a sliding surface is created between the stop surface on the axle bolt and the supported bevel gear and, on the other hand, because of the positionally correct assignment of the axle bolt and the cage, sliding movement of the cage is prevented so that no additional positioning expenditures are required during the assembly.
The assembly of the differential is further facilitated if one centering sleeve, respectively, is supported on the case. The centering sleeve projects through the cage and centers it and the differential bevel gear in the correct position. On the one hand, this prevents the cage from turning and, on the other hand, an intermediate constructional unit can be created which, after the installation into the case, is arranged in the correct position and is torsionally secured and therefore facilitates the installation of the axle shafts.
By using a sliding cup arrangement between the cage and the axle shaft gears, the gear's running behavior can be improved by a friction reduction. At the same time, an improved plane support of the axle shaft gears is obtained on the cage.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.